What it is and what it does
The Siemens 3RT1045-1AN24 is a SIRIUS power contactor, frame size S3, designed for switching motor loads in industrial control panels. It's rated for 45 kW at 500 V and 21.1 kW at 690 V, which tells you it handles the heavy lifting on a pump, conveyor, or compressor circuit. The screw-type terminals on the main current circuit accept solid wire up to 4 mm² and stranded up to 50 mm², so it's ready for the wire sizes you'd expect on a 45 kW motor feed.
Mounting and integration
Mounts via screw or snap-on onto 35 mm and 75 mm standard DIN rail. Side-by-side mounting is supported, so you can pack multiple contactors in a row without derating for heat buildup — useful when you're squeezing a motor control center into a tight enclosure. The front carries IP20 protection with the cover or box terminal installed; the terminal body itself is IP00, meaning the wiring compartment needs to live inside a panel or enclosure.
Key ratings and what they mean
The mechanical life is listed at 10,000,000 operations typical, which is the expected lifespan before the contactor wears out mechanically — not the electrical switching life under load. The maximum switching frequency in AC-3 duty (motor starting) is 1,000 operations per hour, so it can cycle a motor start every 3.6 seconds continuously without exceeding the design limits. Operating temperature range is -25 to +60 °C, which covers most indoor panel environments but watch the upper end if the enclosure runs hot.
Dimensions and wiring
Dimensions are 146 mm high, 70 mm wide, 188 mm deep — the depth is the dimension that sticks out from the DIN rail, so check your enclosure depth if you're retrofitting into an existing panel. Solid wire capacity goes up to 4 mm² per terminal (two conductors per clamp), and stranded up to 50 mm², which covers the main power feed for a 45 kW motor at 500 V.